Code Manual for CONTAIN 2.0 - Federation of American Scientists

Table 11-1
Example Solution for Flow Path Initial Lengths in the Three-Node
Representation of Suppression Pool Vents Shown in Figure 11-2
Top Flow Path A = 17.8761
L = 4.283
Middle Flow Path A = 17.8761
L = 6.490
Bottom Flow Path A = 17.8761
L = 8.362
A = area (mz), L = inertial length (m), as represented in Equation (11-5), for L{z= 2.10, ~~ =
~,= 1.27, ~, =~,=L~, = 1.52, and A1, =A,, =A,, =51.44 in Equation (11-1)
11.1.2 Dedicated Suppression Pool Vent Flow Model
The vent clearing and gas flow rate modeling for the dedicated model is discussed in this section.
The architecture for this model is different from that of the multi-node model discussed above. First
of all, only one suppression pool vent flow path maybe specified per problem. Secondly, in contrast
to what one might expect, coolant is not actually exchanged between pools in different cells during
the vent clearing process for this model. The reason is that the dedicated model uses only one pool,
that in the wetwell cell, and assumes that this pool spans both the drywell and wetwell sides ~
of the vent. Thus, the wetwell cell geometry and pool inventory should reflect the total pool volume
and cross-section. Thirdly, the vent clearing calculation is carried out internally in the model to
determine a vent clearing time, after which the vent is assumed to be accessible to gas flow. This
vent clearing calculation keeps track of liquid levels that should be present on the @well and
wetwell sides of the vent, on the basis of a quasi-steady liquid flow model. Note, however, that the
wetwell pool level reported in the output is not just that of the wetwell side, but is an average value
taking into account both sides of the vent. Other limitations of the single pool treatment are that gaspool
equilibration in reverse flow is not modeled and flooding of the vent from the @well cell pool,
if any, cannot be modeled properly.
The dedicated suppression pool vent flow path is activated at the global level by the keyword
SPVENT as described in Section 14.2.4.3 and can be used only in conjunction with the implicit flow
solver option. (The implicit flow solver option is specified by the keyword IMPLICIT in the
FLOWS input block, as described in Section 14.2.4.1.) With a vent flow path, two cells are required,
one for the wetwell and one for the drywell. A pool must be specified as part of the lower cell input
of the wetwell cell, and this pool should include both the drywell- and wetwell-side inventory. The
area of the pool specified in the lower cell input for the wetwell cell should include all of the free
surface associated with these inventones. Note that the inventory of aerosols, fission products, and
dispersed core debris that have been scrubbed out of the gas passing through the pool is always
associated with the wetwell pool or wetwell lower cell inventory.
Rev O 11 8 6/30/97